MadSci Network: Chemistry

Re: Does aluminum cause or help prevent silver oxidation? What metal does?

Date: Sun Feb 15 15:34:58 2009
Posted By: Cesar Prado-Fdez, Secondary School Teacher, Science
Area of science: Chemistry
ID: 1234115637.Ch


This is the basis of electrochemistry. This is, electricity and chemistry
going together: using chemistry to produce electricity and using
electricity to produce a chemical reaction.

In electrochemistry we will always find that there is one species that
losses electrons (gets oxidized), electrons that will be gained by another
one (which gets reduced, we say). That is why we call these redox (RED for
reduction, OX for oxidation) reactions.

How easy or how hard is for the first species to loss electrons (or to gain
them instead) when compared with the other one will determine their
behavior as species to be respectively oxidized or reduced. We can
translate into numbers the behavior of every chemical species (element,
molecule or ion) in order to make the comparison. This number is the
Reduction Potential [1]. With the reduction potential we can compare the
the two elements to see which one will get reduced and which one oxidized [2-3]

The rule is that the species with a more positive reduction potential will
get reduced whilst the more negative value will be oxidized, whenever we
put them in contact.

The reduction potentials for silver and aluminium are:

Silver     +0.80 V [2]
Aluminium  -1.66 V [4]

Therefore we can say that silver will be protected by aluminium because it
will be the second of the metals the one that will get oxidized and not the

[3]Handbook of Chemistry and Physics: 88th Edition

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